The guitar, whether electric or acoustic, is the primary instrument of rock music, but also flamenco, jazz, blues, country, and many forms of pop. It can also be a solo classical instrument. Guitars may be played acoustically, where the tone is produced by vibration of the strings and modulated by the hollow body, or they may rely on an amplifier that can electronically manipulate tone. Such electric guitars were introduced in the 1930's, and they have continued to have a profound influence on popular culture since then.

Gibson Les Paul Electric guitars can have solid, semi-hollow, or hollow bodies, and produce little sound without amplification. Electromagnetic pickups convert the vibration of the steel strings into electrical signals, which are fed to an amplifier through a cable or radio transmitter. The sound is frequently modified by other electronic devices or the natural distortion of valves (vacuum tubes) in the amplifier. There are two main types of pickup, single and double coil (or humbucker), each of which can be passive or active.

The electric guitar is used extensively in jazz, blues, and rock and roll. The first successful magnetic pickup for a guitar was invented by George Beauchamp, and incorporated into the 1931 Ro-Pat-In (later Rickenbacker) 'Frying Pan' lap steel; other manufacturers, notably Gibson, soon began to install pickups in archtop models. After World War II the completely solid-body electric was popularized by Gibson in collaboration with Les Paul, and independently by Leo Fender of Fender Music. The lower fretboard action (the height of the strings from the fingerboard), lighter (thinner) strings, and its electrical amplification lend the electric guitar to some techniques which are less frequently used on acoustic guitars. These include tapping, extensive use of legato through pull-offs and hammer-ons (also known as slurs), pinch harmonics, volume swells, and use of a tremolo arm or effects pedals.

In acoustic guitars, string vibration is transmitted through the bridge and saddle to the body via sound board. The sound board is typically made of tone woods such as spruce or cedar. Timbers for tone woods are chosen for both strength and ability to transfer mechanical energy from the strings to the air within the guitar body. Sound is further shaped by the characteristics of the guitar body's resonant cavity.

In electric guitars, transducers known as pickups convert string vibration to an electric signal, which in turn is amplified and fed to speakers, which vibrate the air to produce the sounds we hear. Nevertheless, the body of the electric guitar still performs a role in shaping the resultant tonal signature.

In an acoustic instrument, the body of the guitar is a major determinant of the overall sound quality. The guitar top, or soundboard, is a finely crafted and engineered element made of tonewoods such as spruce and red cedar. This thin piece of wood, often only 2 or 3 mm thick, is strengthened by differing types of internal bracing. The top is considered by many luthiers to be the dominant factor in determining the sound quality. The majority of the instrument's sound is heard through the vibration of the guitar top as the energy of the vibrating strings is transferred to it.